<?php

namespace Guyan\JWT;

use ArrayAccess;
use DateTime;
use DomainException;
use Exception;
use InvalidArgumentException;
use OpenSSLAsymmetricKey;
use UnexpectedValueException;

/**
 * JSON Web Token implementation, based on this spec:
 * https://tools.ietf.org/html/rfc7519
 *
 * PHP version 5
 *
 * @category Authentication
 * @package  Authentication_JWT
 * @author   Neuman Vong <neuman@twilio.com>
 * @author   Anant Narayanan <anant@php.net>
 * @license  http://opensource.org/licenses/BSD-3-Clause 3-clause BSD
 * @link     https://github.com/firebase/php-jwt
 */
class JWT {
	const ASN1_INTEGER = 0x02;
	const ASN1_SEQUENCE = 0x10;
	const ASN1_BIT_STRING = 0x03;

	/**
	 * When checking nbf, iat or expiration times,
	 * we want to provide some extra leeway time to
	 * account for clock skew.
	 */
	public static $leeway = 0;

	/**
	 * Allow the current timestamp to be specified.
	 * Useful for fixing a value within unit testing.
	 *
	 * Will default to PHP time() value if null.
	 */
	public static $timestamp = null;

	public static $supported_algs = array(
		'ES384' => array('openssl', 'SHA384'),
		'ES256' => array('openssl', 'SHA256'),
		'HS256' => array('hash_hmac', 'SHA256'),
		'HS384' => array('hash_hmac', 'SHA384'),
		'HS512' => array('hash_hmac', 'SHA512'),
		'RS256' => array('openssl', 'SHA256'),
		'RS384' => array('openssl', 'SHA384'),
		'RS512' => array('openssl', 'SHA512'),
		'EdDSA' => array('sodium_crypto', 'EdDSA'),
	);

	/**
	 * Decodes a JWT string into a PHP object.
	 *
	 * @param string                    $jwt            The JWT
	 * @param Key|array<Key>|mixed      $keyOrKeyArray  The Key or array of Key objects.
	 *                                                  If the algorithm used is asymmetric, this is the public key
	 *                                                  Each Key object contains an algorithm and matching key.
	 *                                                  Supported algorithms are 'ES384','ES256', 'HS256', 'HS384',
	 *                                                  'HS512', 'RS256', 'RS384', and 'RS512'
	 * @param array                     $allowed_algs   [DEPRECATED] List of supported verification algorithms. Only
	 *                                                  should be used for backwards  compatibility.
	 *
	 * @return object The JWT's payload as a PHP object
	 *
	 * @throws InvalidArgumentException     Provided JWT was empty
	 * @throws UnexpectedValueException     Provided JWT was invalid
	 * @throws SignatureInvalidException    Provided JWT was invalid because the signature verification failed
	 * @throws BeforeValidException         Provided JWT is trying to be used before it's eligible as defined by 'nbf'
	 * @throws BeforeValidException         Provided JWT is trying to be used before it's been created as defined by 'iat'
	 * @throws ExpiredException             Provided JWT has since expired, as defined by the 'exp' claim
	 *
	 * @uses jsonDecode
	 * @uses urlsafeB64Decode
	 */
	public static function decode($jwt, $keyOrKeyArray, array $allowed_algs = array()) {
		$timestamp = \is_null(static::$timestamp) ? \time() : static::$timestamp;

		if (empty($keyOrKeyArray)) {
			throw new InvalidArgumentException('Key may not be empty');
		}
		$tks = \explode('.', $jwt);
		if (\count($tks) != 3) {
			throw new UnexpectedValueException('Wrong number of segments');
		}
		list($headb64, $bodyb64, $cryptob64) = $tks;
		if (null === ($header = static::jsonDecode(static::urlsafeB64Decode($headb64)))) {
			throw new UnexpectedValueException('Invalid header encoding');
		}
		if (null === $payload = static::jsonDecode(static::urlsafeB64Decode($bodyb64))) {
			throw new UnexpectedValueException('Invalid claims encoding');
		}
		if (false === ($sig = static::urlsafeB64Decode($cryptob64))) {
			throw new UnexpectedValueException('Invalid signature encoding');
		}
		if (empty($header->alg)) {
			throw new UnexpectedValueException('Empty algorithm');
		}
		if (empty(static::$supported_algs[$header->alg])) {
			throw new UnexpectedValueException('Algorithm not supported');
		}

		list($keyMaterial, $algorithm) = self::getKeyMaterialAndAlgorithm(
			$keyOrKeyArray,
			empty($header->kid) ? null : $header->kid
		);

		if (empty($algorithm)) {
			// Use deprecated "allowed_algs" to determine if the algorithm is supported.
			// This opens up the possibility of an attack in some implementations.
			// @see https://github.com/firebase/php-jwt/issues/351
			if (!\in_array($header->alg, $allowed_algs)) {
				throw new UnexpectedValueException('Algorithm not allowed');
			}
		} else {
			// Check the algorithm
			if (!self::constantTimeEquals($algorithm, $header->alg)) {
				// See issue #351
				throw new UnexpectedValueException('Incorrect key for this algorithm');
			}
		}
		if ($header->alg === 'ES256' || $header->alg === 'ES384') {
			// OpenSSL expects an ASN.1 DER sequence for ES256/ES384 signatures
			$sig = self::signatureToDER($sig);
		}

		if (!static::verify("$headb64.$bodyb64", $sig, $keyMaterial, $header->alg)) {
			throw new SignatureInvalidException('Signature verification failed');
		}

		// Check the nbf if it is defined. This is the time that the
		// token can actually be used. If it's not yet that time, abort.
		if (isset($payload->nbf) && $payload->nbf > ($timestamp+static::$leeway)) {
			throw new BeforeValidException(
				'Cannot handle token prior to ' . \date(DateTime::ISO8601, $payload->nbf)
			);
		}

		// Check that this token has been created before 'now'. This prevents
		// using tokens that have been created for later use (and haven't
		// correctly used the nbf claim).
		if (isset($payload->iat) && $payload->iat > ($timestamp+static::$leeway)) {
			throw new BeforeValidException(
				'Cannot handle token prior to ' . \date(DateTime::ISO8601, $payload->iat)
			);
		}

		// Check if this token has expired.
		if (isset($payload->exp) && ($timestamp-static::$leeway) >= $payload->exp) {
			throw new ExpiredException('Expired token');
		}

		return $payload;
	}

	/**
	 * Converts and signs a PHP object or array into a JWT string.
	 *
	 * @param object|array      $payload    PHP object or array
	 * @param string|resource   $key        The secret key.
	 *                                      If the algorithm used is asymmetric, this is the private key
	 * @param string            $alg        The signing algorithm.
	 *                                      Supported algorithms are 'ES384','ES256', 'HS256', 'HS384',
	 *                                      'HS512', 'RS256', 'RS384', and 'RS512'
	 * @param mixed             $keyId
	 * @param array             $head       An array with header elements to attach
	 *
	 * @return string A signed JWT
	 *
	 * @uses jsonEncode
	 * @uses urlsafeB64Encode
	 */
	public static function encode($payload, $key, $alg = 'HS256', $keyId = null, $head = null) {
		$header = array('typ' => 'JWT', 'alg' => $alg);
		if ($keyId !== null) {
			$header['kid'] = $keyId;
		}
		if (isset($head) && \is_array($head)) {
			$header = \array_merge($head, $header);
		}
		$segments = array();
		$segments[] = static::urlsafeB64Encode(static::jsonEncode($header));
		$segments[] = static::urlsafeB64Encode(static::jsonEncode($payload));
		$signing_input = \implode('.', $segments);

		$signature = static::sign($signing_input, $key, $alg);
		$segments[] = static::urlsafeB64Encode($signature);

		return \implode('.', $segments);
	}

	/**
	 * Sign a string with a given key and algorithm.
	 *
	 * @param string            $msg    The message to sign
	 * @param string|resource   $key    The secret key
	 * @param string            $alg    The signing algorithm.
	 *                                  Supported algorithms are 'ES384','ES256', 'HS256', 'HS384',
	 *                                  'HS512', 'RS256', 'RS384', and 'RS512'
	 *
	 * @return string An encrypted message
	 *
	 * @throws DomainException Unsupported algorithm or bad key was specified
	 */
	public static function sign($msg, $key, $alg = 'HS256') {
		if (empty(static::$supported_algs[$alg])) {
			throw new DomainException('Algorithm not supported');
		}
		list($function, $algorithm) = static::$supported_algs[$alg];
		switch ($function) {
		case 'hash_hmac':
			return \hash_hmac($algorithm, $msg, $key, true);
		case 'openssl':
			$signature = '';
			$success = \openssl_sign($msg, $signature, $key, $algorithm);
			if (!$success) {
				throw new DomainException("OpenSSL unable to sign data");
			}
			if ($alg === 'ES256') {
				$signature = self::signatureFromDER($signature, 256);
			} elseif ($alg === 'ES384') {
				$signature = self::signatureFromDER($signature, 384);
			}
			return $signature;
		case 'sodium_crypto':
			if (!function_exists('sodium_crypto_sign_detached')) {
				throw new DomainException('libsodium is not available');
			}
			try {
				// The last non-empty line is used as the key.
				$lines = array_filter(explode("\n", $key));
				$key = base64_decode(end($lines));
				return sodium_crypto_sign_detached($msg, $key);
			} catch (Exception $e) {
				throw new DomainException($e->getMessage(), 0, $e);
			}
		}
	}

	/**
	 * Verify a signature with the message, key and method. Not all methods
	 * are symmetric, so we must have a separate verify and sign method.
	 *
	 * @param string            $msg        The original message (header and body)
	 * @param string            $signature  The original signature
	 * @param string|resource   $key        For HS*, a string key works. for RS*, must be a resource of an openssl public key
	 * @param string            $alg        The algorithm
	 *
	 * @return bool
	 *
	 * @throws DomainException Invalid Algorithm, bad key, or OpenSSL failure
	 */
	private static function verify($msg, $signature, $key, $alg) {
		if (empty(static::$supported_algs[$alg])) {
			throw new DomainException('Algorithm not supported');
		}

		list($function, $algorithm) = static::$supported_algs[$alg];
		switch ($function) {
		case 'openssl':
			$success = \openssl_verify($msg, $signature, $key, $algorithm);
			if ($success === 1) {
				return true;
			} elseif ($success === 0) {
				return false;
			}
			// returns 1 on success, 0 on failure, -1 on error.
			throw new DomainException(
				'OpenSSL error: ' . \openssl_error_string()
			);
		case 'sodium_crypto':
			if (!function_exists('sodium_crypto_sign_verify_detached')) {
				throw new DomainException('libsodium is not available');
			}
			try {
				// The last non-empty line is used as the key.
				$lines = array_filter(explode("\n", $key));
				$key = base64_decode(end($lines));
				return sodium_crypto_sign_verify_detached($signature, $msg, $key);
			} catch (Exception $e) {
				throw new DomainException($e->getMessage(), 0, $e);
			}
		case 'hash_hmac':
		default:
			$hash = \hash_hmac($algorithm, $msg, $key, true);
			return self::constantTimeEquals($signature, $hash);
		}
	}

	/**
	 * Decode a JSON string into a PHP object.
	 *
	 * @param string $input JSON string
	 *
	 * @return object Object representation of JSON string
	 *
	 * @throws DomainException Provided string was invalid JSON
	 */
	public static function jsonDecode($input) {
		if (\version_compare(PHP_VERSION, '5.4.0', '>=') && !(\defined('JSON_C_VERSION') && PHP_INT_SIZE > 4)) {
			/** In PHP >=5.4.0, json_decode() accepts an options parameter, that allows you
			 * to specify that large ints (like Steam Transaction IDs) should be treated as
			 * strings, rather than the PHP default behaviour of converting them to floats.
			 */
			$obj = \json_decode($input, false, 512, JSON_BIGINT_AS_STRING);
		} else {
			/** Not all servers will support that, however, so for older versions we must
			 * manually detect large ints in the JSON string and quote them (thus converting
			 *them to strings) before decoding, hence the preg_replace() call.
			 */
			$max_int_length = \strlen((string) PHP_INT_MAX) - 1;
			$json_without_bigints = \preg_replace('/:\s*(-?\d{' . $max_int_length . ',})/', ': "$1"', $input);
			$obj = \json_decode($json_without_bigints);
		}

		if ($errno = \json_last_error()) {
			static::handleJsonError($errno);
		} elseif ($obj === null && $input !== 'null') {
			throw new DomainException('Null result with non-null input');
		}
		return $obj;
	}

	/**
	 * Encode a PHP object into a JSON string.
	 *
	 * @param object|array $input A PHP object or array
	 *
	 * @return string JSON representation of the PHP object or array
	 *
	 * @throws DomainException Provided object could not be encoded to valid JSON
	 */
	public static function jsonEncode($input) {
		$json = \json_encode($input);
		if ($errno = \json_last_error()) {
			static::handleJsonError($errno);
		} elseif ($json === 'null' && $input !== null) {
			throw new DomainException('Null result with non-null input');
		}
		return $json;
	}

	/**
	 * Decode a string with URL-safe Base64.
	 *
	 * @param string $input A Base64 encoded string
	 *
	 * @return string A decoded string
	 */
	public static function urlsafeB64Decode($input) {
		$remainder = \strlen($input) % 4;
		if ($remainder) {
			$padlen = 4 - $remainder;
			$input .= \str_repeat('=', $padlen);
		}
		return \base64_decode(\strtr($input, '-_', '+/'));
	}

	/**
	 * Encode a string with URL-safe Base64.
	 *
	 * @param string $input The string you want encoded
	 *
	 * @return string The base64 encode of what you passed in
	 */
	public static function urlsafeB64Encode($input) {
		return \str_replace('=', '', \strtr(\base64_encode($input), '+/', '-_'));
	}

	/**
	 * Determine if an algorithm has been provided for each Key
	 *
	 * @param Key|array<Key>|mixed $keyOrKeyArray
	 * @param string|null $kid
	 *
	 * @throws UnexpectedValueException
	 *
	 * @return array containing the keyMaterial and algorithm
	 */
	private static function getKeyMaterialAndAlgorithm($keyOrKeyArray, $kid = null) {
		if (
			is_string($keyOrKeyArray)
			|| is_resource($keyOrKeyArray)
			|| $keyOrKeyArray instanceof OpenSSLAsymmetricKey
		) {
			return array($keyOrKeyArray, null);
		}

		if ($keyOrKeyArray instanceof Key) {
			return array($keyOrKeyArray->getKeyMaterial(), $keyOrKeyArray->getAlgorithm());
		}

		if (is_array($keyOrKeyArray) || $keyOrKeyArray instanceof ArrayAccess) {
			if (!isset($kid)) {
				throw new UnexpectedValueException('"kid" empty, unable to lookup correct key');
			}
			if (!isset($keyOrKeyArray[$kid])) {
				throw new UnexpectedValueException('"kid" invalid, unable to lookup correct key');
			}

			$key = $keyOrKeyArray[$kid];

			if ($key instanceof Key) {
				return array($key->getKeyMaterial(), $key->getAlgorithm());
			}

			return array($key, null);
		}

		throw new UnexpectedValueException(
			'$keyOrKeyArray must be a string|resource key, an array of string|resource keys, '
			. 'an instance of Firebase\JWT\Key key or an array of Firebase\JWT\Key keys'
		);
	}

	/**
	 * @param string $left
	 * @param string $right
	 * @return bool
	 */
	public static function constantTimeEquals($left, $right) {
		if (\function_exists('hash_equals')) {
			return \hash_equals($left, $right);
		}
		$len = \min(static::safeStrlen($left), static::safeStrlen($right));

		$status = 0;
		for ($i = 0; $i < $len; $i++) {
			$status |= (\ord($left[$i]) ^ \ord($right[$i]));
		}
		$status |= (static::safeStrlen($left) ^ static::safeStrlen($right));

		return ($status === 0);
	}

	/**
	 * Helper method to create a JSON error.
	 *
	 * @param int $errno An error number from json_last_error()
	 *
	 * @return void
	 */
	private static function handleJsonError($errno) {
		$messages = array(
			JSON_ERROR_DEPTH => 'Maximum stack depth exceeded',
			JSON_ERROR_STATE_MISMATCH => 'Invalid or malformed JSON',
			JSON_ERROR_CTRL_CHAR => 'Unexpected control character found',
			JSON_ERROR_SYNTAX => 'Syntax error, malformed JSON',
			JSON_ERROR_UTF8 => 'Malformed UTF-8 characters', //PHP >= 5.3.3
		);
		throw new DomainException(
			isset($messages[$errno])
			? $messages[$errno]
			: 'Unknown JSON error: ' . $errno
		);
	}

	/**
	 * Get the number of bytes in cryptographic strings.
	 *
	 * @param string $str
	 *
	 * @return int
	 */
	private static function safeStrlen($str) {
		if (\function_exists('mb_strlen')) {
			return \mb_strlen($str, '8bit');
		}
		return \strlen($str);
	}

	/**
	 * Convert an ECDSA signature to an ASN.1 DER sequence
	 *
	 * @param   string $sig The ECDSA signature to convert
	 * @return  string The encoded DER object
	 */
	private static function signatureToDER($sig) {
		// Separate the signature into r-value and s-value
		list($r, $s) = \str_split($sig, (int) (\strlen($sig) / 2));

		// Trim leading zeros
		$r = \ltrim($r, "\x00");
		$s = \ltrim($s, "\x00");

		// Convert r-value and s-value from unsigned big-endian integers to
		// signed two's complement
		if (\ord($r[0]) > 0x7f) {
			$r = "\x00" . $r;
		}
		if (\ord($s[0]) > 0x7f) {
			$s = "\x00" . $s;
		}

		return self::encodeDER(
			self::ASN1_SEQUENCE,
			self::encodeDER(self::ASN1_INTEGER, $r) .
			self::encodeDER(self::ASN1_INTEGER, $s)
		);
	}

	/**
	 * Encodes a value into a DER object.
	 *
	 * @param   int     $type DER tag
	 * @param   string  $value the value to encode
	 * @return  string  the encoded object
	 */
	private static function encodeDER($type, $value) {
		$tag_header = 0;
		if ($type === self::ASN1_SEQUENCE) {
			$tag_header |= 0x20;
		}

		// Type
		$der = \chr($tag_header | $type);

		// Length
		$der .= \chr(\strlen($value));

		return $der . $value;
	}

	/**
	 * Encodes signature from a DER object.
	 *
	 * @param   string  $der binary signature in DER format
	 * @param   int     $keySize the number of bits in the key
	 * @return  string  the signature
	 */
	private static function signatureFromDER($der, $keySize) {
		// OpenSSL returns the ECDSA signatures as a binary ASN.1 DER SEQUENCE
		list($offset, $_) = self::readDER($der);
		list($offset, $r) = self::readDER($der, $offset);
		list($offset, $s) = self::readDER($der, $offset);

		// Convert r-value and s-value from signed two's compliment to unsigned
		// big-endian integers
		$r = \ltrim($r, "\x00");
		$s = \ltrim($s, "\x00");

		// Pad out r and s so that they are $keySize bits long
		$r = \str_pad($r, $keySize / 8, "\x00", STR_PAD_LEFT);
		$s = \str_pad($s, $keySize / 8, "\x00", STR_PAD_LEFT);

		return $r . $s;
	}

	/**
	 * Reads binary DER-encoded data and decodes into a single object
	 *
	 * @param string $der the binary data in DER format
	 * @param int $offset the offset of the data stream containing the object
	 * to decode
	 * @return array [$offset, $data] the new offset and the decoded object
	 */
	private static function readDER($der, $offset = 0) {
		$pos = $offset;
		$size = \strlen($der);
		$constructed = (\ord($der[$pos]) >> 5) & 0x01;
		$type = \ord($der[$pos++]) & 0x1f;

		// Length
		$len = \ord($der[$pos++]);
		if ($len & 0x80) {
			$n = $len & 0x1f;
			$len = 0;
			while ($n-- && $pos < $size) {
				$len = ($len << 8) | \ord($der[$pos++]);
			}
		}

		// Value
		if ($type == self::ASN1_BIT_STRING) {
			$pos++; // Skip the first contents octet (padding indicator)
			$data = \substr($der, $pos, $len - 1);
			$pos += $len - 1;
		} elseif (!$constructed) {
			$data = \substr($der, $pos, $len);
			$pos += $len;
		} else {
			$data = null;
		}

		return array($pos, $data);
	}
}
